Predicting Confrontation Naming in the Logopenic Variant of Primary Progressive Aphasia

Abstract

Naming difficulties are prominent and pervasive in the logopenic variant of primary progressive aphasia (lvPPA) and are related to its underlying deficits in phonological processing. Importantly, some words appear to be more vulnerable to deterioration than others. We hypothesize that these differences can be explained, in part, by the unique psycholinguistic properties of words. Our study investigated the role of psycholinguistic properties of words, along with their underlying psycholinguistic factors, on confrontation naming performance in individuals with lvPPA. Naming accuracy data were collected from 10 individuals with lvPPA using the Boston Naming Test (BNT). For each test item, values were extracted for frequency, contextual diversity, age of acquisition (AoA), word length, phonological neighborhood density (PND), concreteness, semantic neighborhood density (SND), familiarity, arousal, and valence. We examined the effects of these psycholinguistic properties on naming accuracy using logistic regression analyses at the individual level and multiple linear regression analysis at the group level. Age of acquisition emerged as the strongest psycholinguistic predictor of naming accuracy in lvPPA at both the individual and group levels. Given that AoA and frequency are highly correlated, mediation analyses were performed to identify the relationships between AoA, frequency, and naming accuracy. The influence of AoA on naming accuracy was only partially mediated by frequency. Principal component analysis was performed to extract fundamental factors of the psycholinguistic properties. Four principal psycholinguistic factors were extracted. These were interpreted as lexical-semantic usage, phonological simplicity, semantic disembodiment, and semantic pleasantness. These factor scores were entered into multiple linear and logistic regression analyses to investigate their relative contribution to naming accuracy in lvPPA. Results indicated that lexical-semantic usage, semantic disembodiment, and semantic pleasantness predicted naming performance at the group level. Additionally, lexical-semantic usage and semantic disembodiment emerged as significant predictors at the individual level. The effects of the psycholinguistic properties and their factors and their theoretical implications are discussed in the context of phonological deficits in lvPPA and models of word naming.